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#26 2020-04-25 08:35:57

tahanson43206
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Registered: 2018-04-27
Posts: 7,981

Re: Physics Topics

This is a new subset of the Physics topic.

A problem addressed by those who seek to design a space elevator is the limit of chemical bonds holding atoms together in materials.

At present (with the possible exception of carbon filaments) no material has the cohesive strength to withstand the forces at work in the environment of Earth.  Existing materials can handle deployment on the Moon, and perhaps other locations, such as Terraformer's Ceres concept.

As the focus of a new subset of the Physics topic, this post introduces the question of which primary forces are involved in the familiar chemical bonds that provide the cohesion upon which the entire world (and certainly the entire humanly constructed part of it) depend.

I've never had occasion to think about this before, except in the most casual manner.  I'd assumed (quite naively) that electrostatic attraction is the sole force comprising the force(s) that support chemical cohesion.

That (naive, I'm sure) impression came from the electrostatic attraction between electrons moving around the nucleus, and the protons in the nucleus of each atom.  However, there may be (and probably is) much more at work than simple electrostatic attraction.

It had occurred to me to wonder if magnetic force is involved at all in defining the strength of materials, and if the power of that force could be artificially increased to increase the strength of cohesion for a temporary application, such as dropping a cable from a geosynchronous hub to pick up a load from the surface of the Earth.

(th)

Last edited by tahanson43206 (2020-04-25 17:44:14)

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#27 2020-04-25 15:59:25

kbd512
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Registered: 2015-01-02
Posts: 4,893

Re: Physics Topics

tahanson43206,

EMF can actually snap an electrically conductive cable used to raise the orbit of a satellite if it's not strong enough to withstand the strain placed upon it.  We "discovered" this during a Space Shuttle mission to test electrodynamic tether technology created to raise the orbit of satellites without energy input (on our part).  The combination of Earth's magnetic field and moving through that field at orbital velocity would do the work of raising the satellite's orbit.  There's a massive amount of power there- even more than the scientists predicted, hence the snapped tether.  If you search back through the topics, you can see where RobertDyck and others discussed the possibility of using this tech to raise the orbit of a spacecraft from LEO to GEO without any humans onboard (to avoid exposure to the radiation maelstrom encountered in orbits above where ISS is located.  Given newer and much stronger CNT conductors that didn't exist when that STS mission took place, that technology should be revisited.

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#28 2020-04-25 18:22:57

tahanson43206
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Registered: 2018-04-27
Posts: 7,981

Re: Physics Topics

This is a continuation of Post #25

In this post, I am continuing an attempt to understand the vision of Void, to launch a vehicle from the Moon to escape velocity, using steam.

Because of limitations of the Physics 101 calculator, I've gone online and asked for help with the Rocket Equation:

Working the Steam Rocket problem using online resources:

https://www.omnicalculator.com/physics/ … t-equation

Ideal Rocket Calculator

Effective exhaust velocity
3,433.6  << computed by program
m/s

Initial mass
10,000 << arbitrary vehicle size chosen for problem
kg

Final mass
5,000 << arbitrary allocation to propellant of 50%
kg

Change of velocity
2380 << Escape velocity from Moon
m/s

Reset defaults Send this result

https://www.omnicalculator.com/physics/rocket-thrust

Redoing rocket-thrust calculation using 3,433.6 exhaust velocity

Effective Velocity: 3,433.6 m/s
Flow area of nozzle: 20 cm^2 (estimate entered by operator)
Mass loss rate: 51.5 kg/s << This is 5000 Kb divided by 97 seconds of launch time
Ambient pressure 0 Pa (Lunar surface)
Pressure at nozzle: 34,084,800 Pa (computed by program) <<== The result of interest: propellant heating chamber (boiler)
Thrust: 245,000 Newtons (from requirements for launch) <<== 72 miles of track at 2.5 G's

Having chosen the size of the nozzle as 20 square centimeters by pulling a number out of thin air, I am looking at a chamber pressure of 34 megaPascals.

Is that a large number, outside the reality of the real world?  I have no idea at this point.

Looking ahead, there is the practical challenge of using energy from some external source to create the internal pressure in the boiler to deliver the thrust needed for this application.  A "traditional" chemical rocket would use oxygen and hydrogen as a means of energy storage in the rocket itself.

Void's proposal is to use external energy to excite the water molecules carried in the propellant tank to such an extent they will hurry out the exhaust at 3,433.6 meters per second at the rate of 51.5 kilograms per second, to deliver 245,000 Newtons of force to the vehicle for 97 seconds.

At this point, I have only the vaguest of ideas how that might be done.

One thing I'm pretty sure is the case ... nothing like that has been done by human beings before.

Edit#1: The Space Shuttle produced water by combustion, and it generated far more thrust for far longer. That was a split water design.

Fortunately, the paper reported earlier, describing a NASA study of the use of a nuclear thermal rocket to achieve exactly what Void proposes, gives some validity to the concept, although it certainly doesn't directly address the problem of how to deliver external energy to the propellant.

It would appear to be time to go back to the NASA paper to try to understand how they planned to heat water to achieve the launch they reported was more cost effective than an equivalent split water design.

Edit#2: For comparison, here is a summary of exhaust velocity for the Space Shuttle Boosters and Main engines:

The Solid Rocket Boosters of the Space Shuttle have an exhaust velocity of 8436 feet per second (2,571 meters per second). By contrast, the main engines of the Shuttle produce 14,590 feet per second (4,447 meters per second).

rocket engine - Centennial of Flightwww.centennialofflight.net › SPACEFLIGHT › rockets

The online Rocket Equation calculator came up with: 3,433.6 exhaust velocity (Meters per second)

Edit#3: The chamber pressure in the Space Shuttle main engines appears to have been significantly lower than the calculator estimate of 34 Megapascals!

The Space Shuttle used a cluster of three RS-25 engines mounted in the stern structure of the orbiter, with fuel being drawn from the external tank.
...
RS-25.
Liquid-fuel engine
Thrust (SL)    418,000 lbf (1,860 kN)
Thrust-to-weight ratio    73.1
Chamber pressure    2,994 psi (20.64 MPa)
Isp (vac.)    452.3 seconds (4.436 km/s)
21 more rows

RS-25 - Wikipedia

Edit#4: The throat area of the Space Shuttle Main Engines is reported to have been 90+ square inches

http://large.stanford.edu/courses/2011/ … TATION.pdf

MAIN COMBUSTION CHAMBER The Main Combustion Chamber (MCC) contains the combustion process, accelerates the gas flow to throat sonic velocity, and initiates the gas expansion process through its diverging section. The expansion ratio of throat to nozzle attach flange is 4.48:1, with the throat area being 93.02 square inches. The chamber includes a liner, jacket, throat ring, coolant inlet manifold, and coolant

I had arbitrarily chosen a throat area of 20 square centimeters in order to persuade the online Rocket Equation calculator to do anything at all.  I'll go back to try a larger throat area, to see if that reduces the chamber pressure from the computed 34 Megapascals

(th)

Last edited by tahanson43206 (2020-04-25 19:53:44)

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#29 2020-04-26 12:46:29

tahanson43206
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Registered: 2018-04-27
Posts: 7,981

Re: Physics Topics

Void has already reported this steam powered asteroid prospector in another topic.

I decided to add this post because the source is phys.org:

https://phys.org/news/2019-01-steam-pro … plore.html

Edit#1:  At some point, in development of Void's vision of a steam rocket to launch a vehicle from the surface of the Moon to lunar escape velocity, it will be necessary to try to understand how external energy could be supplied to a moving vehicle so that liquid water held in a propellant tank is given sufficient energy to produce 245,000 Newtons of thrust.

In a chemical rocket (eg, water split design), the energy needed is stored in the separated Hydrogen and Oxygen components.  When these elements are brought into proximity in a suitable environment, they combine back to water, and release abundant energy in the process.  It is this energy which delivers the high energy steam that then exits the exhaust port.

In Void's vision of a steam rocket, energy is supplied from an external source.

Microwave radiation is a reasonable candidate to be examined to see if it can provide the needed energy inside the boiler.  However, the waves would need to enter the boiler from outside the moving vehicle, and whatever material is used to enclose the boiler would need to be strong enough to withstand the enormous pressure needed to deliver 51.5 kilograms of water through the exhaust port every second, for 97 seconds.

The familiar microwave oven achieves heating of water molecules directly, by manipulating a slight imbalance of electric fields characteristic of the water molecule.

Another candidate method of heating is indirect.  Such a method is used in solar troughs.  These absorb energy from visible light (and infrared light) which passes through the liquid to be heated, and delivers energy to the material comprising the trough itself.  The heated trough then transfers heat energy to the working fluid via convection.

This citation from journals.sagepub.com would appear to indicate that carbon may not be an ideal substance for allowing microwaves to enter the boiler:

Abstract Carbon compounds have high dielectric losses, which means that these materials are heated efficiently by microwave irradiation. Carbon materials can be used as microwave absorbers in polymeric materials that are transparent to microwave irradiation.

Investigating the carbon materials' microwave absorption and ...

Edit#2: The document saved online with this title: /materials-09-00231.pdf

contains a paper by:

Jing Sun 1 , Wenlong Wang 2, * and Qinyan Yue 1, *
School of Environmental Science and Engineering, Shan

Review on Microwave-Matter Interaction
Fundamentals and Efficient Microwave-Associated
Heating Strategies

This 25 page paper appears to be promising for study, based upon reading the abstract.

However, the point that jumped out at me from the Introduction is the idea that water can be heated indirectly by excitation of suspended metal particles in the water.  Void has recently extended his vision of propulsion on the Moon to include Magnesium, which is present on the Moon in abundance.

The propellant which might be given thermal energy by a microwave input could contain a solution of Magnesium particles.  The proposition to be explored in this case, is that the microwave energy might be more efficiently given to the Magnesium than to the water itself. 

Edit#1: In digging a bit further into this 25 page paper, I realized that NewMars forum members could perform actual experiments using home microwave ovens (very carefully please!), by studying this paper.  The hypothesis I am entertaining is that Void's interest in Magnesium in the lunar regolith might lead to a concept for a suspension of nanoparticle sized Magnesium nodules which could more readily accept microwave heating than does water by itself.

The paper describes the use of microwaves to sinter a number of metals (citations go back to 1999).

What is NOT clear at this point is whether substitution of part of the 5000 kg allocated to propellant in the hypothetical Void's Steam Rocket to magnesium in place of water would provide a benefit sufficient to justify the extra effort that would be required.

What ** seems ** to be clear is that metal atoms can be expected to respond to microwave more vigorously than do water molecules, which respond only because of an imbalance of distribution of electric charge in the water molecule.

Single ion impacts a million water molecules -- ScienceDailywww.sciencedaily.com › releases › 2016/04
Apr 8, 2016 - Water molecules are made up of one negatively charged oxygen atom and two positively charged hydrogen atoms. Share: FULL STORY. Water ...

Direction to look: Efficiency of energy transfer to matter via microwave radiation

Another direction to look for Void's Steam Rocket on the Moon is laser heating of materials inside the boiler, which would heat adjacent water by conduction.

In that case, lasers would be stationed along the track, to send pulses of light into windows in the boiler as the vehicle passes by.  That would be similar in concept to electromagnetic coils being energized as a vehicle passes by. 

(th)

Last edited by tahanson43206 (2020-04-27 07:22:35)

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#30 2020-04-26 13:14:03

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,682
Website

Re: Physics Topics

Tahanson43206:

To have a specific impulse you can go play games with,  you MUST have a thrust and a mass flow rate.  There are NO rocket concepts that do not have those two features.  The mass flow rate must be that drawn from storage to create the thrust.  Some rocket concepts draw more flow from storage than actually goes through the thrust production device (usually a nozzle). 

The modeling codes for thermochemistry and rocket performance take no account of that possible difference in mass flows,  or any accounting of the device efficiencies for combustors,  nozzles,  etc. Believe that computer stuff at your own risk,  and it can be a big risk.

With electric propulsion,  thrust is not figured from fluid mechanics.  All the other rockets (so far) use fluid mechanics to create thrust.  (I do NOT count nuclear pulse propulsion as a "rocket".)  The energy release (whatever it is) creates high effective temperature at some high pressure in the essentially-static flow conditions of the chamber.  The chamber temperature and associated gas properties feed into a characteristic velocity c*,  that is theoretically a function of chamber pressure,  and is an ideal upper bound coming from thermochemistry.

The efficiency of a real chamber at creating c* from energy release is termed "c*-efficiency",  which is also a function of chamber pressure Pc,  and potentially some other real-world factors.  Thus actual achieved c* is (at least) a function of chamber pressure.  Field test experience shows quite clearly that the pressure effect is a power law function c* = K Pc^m where the exponent m is empirical,  but is usually between about 0.005 and 0.050.  A good first-cut guess is 0.010.  But real experimental data rules.  Period!

Whatever that chamber pressure Pc is in your rocket engine design,  it controls c*,  and to some extent it controls the thrust coefficient CF.  Thrust coefficient CF is defined to be F/Pc At where At is the nozzle choked throat area.  The other determining factors for CF are the supersonic expansion ratio Ae/At and the ambient backpressure Pb around the nozzle device. If in vacuum,  Pb is 0,  and the expansion ratio Ae/At is the sole determinant.  Excepting for the effect of gas properties.

But,  each propellant identity has its own gas properties,  and for CF,  the gas property of interest is the specific heat ratio.   However,  for most practical chemical designs,  that ratio is pretty near 1.20,  and CF is not critically sensitive to its value.  Only somewhat.  For steam,  it's nearer 1.3.  I'm not sure what the "right" number is for hydrogen gas in a nuclear thermal rocket.  For airbreathing combustion gases,  it  falls in the 1.20-1.30 range,  varying with air/fuel ratio.

The thrust of a nozzle device is two terms:  a momentum term that is nozzle(!) massflow multiplied by the exit velocity,  and a pressure term that is the exit expanded pressure Pe times the exit area Ae of the nozzle device.  In vacuum,  that's all there is,  and thrust F = mdot Ve + Pe Ae.  In an atmosphere at nonzero pressure,  there is a thrust-reducing backpressure term that is the backpressure multiplied by the exit area Pb Ae,  for F = mdot Ve + (Pe - Pb)Ae,  the usual thing you see in textbooks.

What limits thrust is Ve,  in turn limited by just how much expansion Ae/At you can do.  In vacuum,  there are no fundamental limits on Ae/At,  other than diminishing returns,  and (more usually) just how much Ae can you tolerate in your rocket stage design.  That's why in the old days,  rocket vacuum performance was calculated at Ae/At = 40,  and in more recent years at Ae/At = 100.  You simply cannot have a rocket nozzle exit diameter exceeding your stage diameter.  Obviously,  what can feasibly be had is something that shifts with time as technologies evolve.

In an atmosphere,  you are most critically constrained by the ambient backpressure Pb,  as a relative measure to your chamber pressure Pc.  The best possible performance is when your expanded pressure Pe is exactly Pb.  For too much expansion ("overexpanded"),  the Pe-Pb term in thrust is negative because Pe < Pb,  reducing thrust directly.  If it's too low,  the nozzle flow will separate,  really killing any thrust.  For too little expansion ("underexpanded"), while the (Pe-Pb)Ae term is positive,  it is smaller than what you would have gotten from the mdot Ve term directly.  This is exactly why "sea level performance" is figured at Pc = some design value,  and Pb = 14.7 psia.

As it turns out,  the variables commonly used in compressible flow analysis are more useful figuring CF than the primitive variables.  After substitutions,  the thrust equation becomes F = [Pe(1 + etan gam Me^2) - Pb]Ae,  where etan is the nozzle kinetic energy efficiency (primarily a streamline divergence factor off axial),  and "gam" is the gas specific heat ratio.  Substituting for thrust coefficient per its definition,  this becomes CF = [Pe/Pc(1 + etan gam Me^2) - Pb/Pc]Ae/At.  The ratio Pb/Pc comes from your design's Pc and the actual ambient backpressure Pb.  The ratio Pe/Pc and the exit Mach number Me come from your design's Ae/At. 

So you figure CF from Ae/At and gam,  given a Pc and a Pb,  down in an atmosphere at Pb,  or else you figure it from Ae/At and gam out in vacuum,  subject to some (seemingly-arbitrary) limit on Ae/At. Either way,  once you have CF,  you have thrust F = CF Pc At.  The nozzle (!!) massflow that goes with that is mdot = Pc CD At gc / c*.  CD is the nozzle throat discharge efficiency.  "Good" designs are usually near 0.98 = CD.  Orifices are nearer 0.80. 

For many designs,  there will be a massflow that is tapped-off from the chamber to run the pumps,  and which is dumped,  not going through the nozzle at all.  The total massflow drawn from storage is nozzle massflow plus massflow dumped.  The Isp,  that you can play mass ratio/delta-V games with,  is thrust/massflow drawn,  NOT just thrust/nozzle massflow. If ALL the massflow drawn from storage also goes through the nozzle,  then Isp = CF c*/gc applies.  If not,  then you CANNOT use that equation!

There is a compressible analog to the streamtube area-velocity relation that relates exit Mach number Me to Ae/At for any given value of gam.  It is a transcendental solution for Me in terms of input Ae/At.  That relation is:

Ae/At = (1/Me)[TR/(c2)]^exp where c2 = (gam+1)/2 and TR = 1 + c1 Me^2,  where in turn c1 = (gam - 1)/2.  The exponent exp = (gam + 1)/[2(gam - 1)].

Getting the expanded pressure ratio is easy,  once this is solved for Me.  Pc/Pe = TR^exp2,  where exp2 = gam/(gam-1).  Then you invert it to Pe/Pc for use in the CF equation.

This stuff is complicated,  I know,  but there is NO WAY AROUND THAT!  It has been in every compressible fluids or propulsion textbook since the mid 20th century. 

The way I do it for nozzles down in atmospheres is to select a Pc,  compute Pe = Pb,  calculate Pe/Pc,  then Me,  then size Ae/At.  From there for a given propellant I have gam,  and thus I have CF,  which for an input At,  sizes both thrust F and nozzle massflow (via c*).  The engine cycle sizes dumped massflow,  and thus the total massflow drawn from storage,  and thus in turn the Isp that I can play mass ratio/delta-V games with.

Sorry,  I just do not see any shortcut to the physics.  And what I have outlined applies to Void's steam rocket,  as well as all liquids,  solids,  and hybrids.  It applies to nuclear thermal,  as well. 

I've talked with Bob Truax,  who did the steam rocket for Evel Knievel's "Sky Cycle" attempt at the Snake River canyon jump.  He did that design with the same physics that I use.  The failure wasn't the rocket,  it was control over the abort chute.   

GW

Last edited by GW Johnson (2020-04-26 14:27:41)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#31 2020-04-27 06:22:58

tahanson43206
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Registered: 2018-04-27
Posts: 7,981

Re: Physics Topics

For GW Johnson re #30

SearchTerm:SpecificImpulse
SearchTerm:ISP
SearchTerm:SteamRocket

Direct link: http://newmars.com/forums/viewtopic.php … 28#p167628

Last edited by tahanson43206 (2020-04-27 06:23:43)

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#32 2020-04-27 06:33:21

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 7,981

Re: Physics Topics

For kbd512 re #27

Thank you for taking a look at the new subtopic.  I haven't come up with a short descriptor for it.

Your observations and references are helpful.

It is in danger of becoming lost in the much larger discussion of how Void's steam rocket might work on the Moon.

If there is anyone on the forum, or perhaps thinking about joining the forum, there may be something to think about in kbd512's reply and the original post.

As a first cut, I ** think ** the question comes down to: how does cohesion work?

Everything in our (known) Universe depends upon it.

Electrostatic force pulling electrons toward protons is (to my way of thinking) clearly a major component.

The question I am asking is whether magnetic force plays a substantial role, or any role at all.

kbd512's observation shows that the forces of cohesion can be disrupted by high voltage.

That in itself is well known.  What kbd512's post reminds is that high voltages can be generated in the rarefied atmosphere of Low Earth Orbit.

Edit#1: Here is a classical example of circular thinking (self-referential logic):

The word cohesion comes from the Latin word cohaerere, which means "to stick together or stay together." In chemistry, cohesion is a measure of how well molecules stick to each other or group together. It is caused by the cohesive attractive force between like molecules.Jul 17, 2019

Cohesion Definition and Examples in Chemistry - ThoughtCo

I'd like to think this forum can do better than that.

(th)

Last edited by tahanson43206 (2020-04-27 06:51:41)

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#33 2020-04-27 08:27:11

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,682
Website

Re: Physics Topics

If memory serves,  Truax's steam rocket for Knievel operated at about 300 psia (roughly 20 bar),  and gave an Isp ~ 80 sec,  about like a home firework. 

They used direct heating,  I think with electric heating elements,  of water under chamber pressure,  sealed in the tank.  Memory may not serve,  but I think the temperature of the hot water was around 300 F. 

"Ignition" of the rocket was by burst diaphragm in the nozzle. Throat or entrance or exit,  I no longer remember.  Exposed to the lower pressure at the nozzle,  the overheated water flashes into steam,  at a rate defined by throat size and chamber pressure,  matching flow rate such that the chamber pressure is maintained by the flow rate.  That is standard steam table stuff. 

The advantage is the utter simplicity,  given that one is competent at hot pressure vessel design.  The disadvantage is the low performance,  meaning the low Isp.  That can be raised by going to higher chamber pressures and temperatures per the steam tables,  but it is never all that high, to the best of my poor knowledge. 

Truax picked the low numbers that he did because 80 sec Isp was sufficient to get Knievel across the canyon if nothing went wrong.  It did go wrong,  because the slo-mo video clearly shows the chute deploying at launch,  when it wasn't supposed to until after apogee across the canyon. The rocket itself worked just as designed.

It takes a lot of energy added to the water to get it to flash into steam at high rates like that.  I rather doubt the validity of any scheme claiming to do that real-time as the device flies!  You add the energy to the water (by whatever means) slowly,  before you launch. 

You look in the steam tables to identify compressed liquid temperature as a function of your selected chamber pressure.  That is what water will do,  you are NOT free to impose other design values!  The velocity of the exiting steam is limited by the enthalpy of the compressed heated water that you can achieve.  Simple as that.

You look at chamber conditions,  throat conditions,  and exit conditions with thermodynamics at the one design mass flow rate.  That sets the properties at each station,  including velocity and density,  which sets the proportions of the nozzle areas. 

Everthing scales from the throat size:  a big throat is a low burn time and a big thrust,  with the fastest flash-off rate.  A small throat is a long burn time and a low thrust,  at a slow flash-off rate.  But total impulse is fixed by the quantity of water and its compressed hot liquid conditions prior to launch.

There's no free lunch here.  But if you have a source of water to mine,  and a source of energy to heat compressed liquid,  then yes,  you can fly around in short bursts on a steam rocket,  just as long you can find water deposits to mine.  It is inherently inefficient,  but you never run out of refueling "stations",  unless you happen to leave the environments where the deposits really are. 

BTW,  I predict that smaller asteroids will prove to be rather dry.  Only the big ones (near dwarf planet size) seem to be wet.  Most of the moon seems to be dry as well.  But there's quite a bit of ice on Mars,  not everywhere,  but fairly widespread. 

The steam rocket is a possible way to power a rocket hopper craft point-to-point around the surface of Mars. Possible.  Desirable?  That remains to be seen.  You have to take your heater and energy supply with you.  That means they must be small,  and so will take a long time to heat up the water for the next hop.  And at such low performance,  the hops are short.  No way around that.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#34 2020-04-27 09:14:14

Void
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Registered: 2011-12-29
Posts: 3,988

Re: Physics Topics

Hi GW.  Think I should clarify what I was attempting to be up to.

Umm....  There is some evidence that some rubble pile asteroids even though dry will have clays, an so hydrated minerals.  So they are as per ice, dry,  but supposedly it may be possible to bake water out of the clays.

But for what I was after for the Moon, I was pondering several potential options for propulsion concerning Magnesium and an Oxidizer.

To a degree, I was attempting to combine the power from preheated materials, where that heat can contribute to a propulsive exhaust, but I also intended to have a chemical reaction by way of burning Magnesium with an Oxidizer.

Two methods I am somewhat currently interested in would be using molten Magnesium, ideally as close to the boiling point of Magnesium as is do-able.

1) Molten Magnesium as the fuel.  Water steam as the Oxidizer.

2) Molten Magnesium as the fuel.  A temperate fluid mix of water and Hydrogen Peroxide as the Oxidizer.

I realize that to do this as in cold propellant engines, some method is required to push these fluids into the combustion chamber(s).

Rocket Labs uses batteries to power that pumping method, else an engine would have to use one of the various schemes similar to engines that have used Hydrogen, or Methane, and Oxygen.

It is a tall order, and I don't expect it to be implemented anytime soon.

But the difference is I want to work with hot a thermally hot fuel, (Liquid Magnesium), and either hot steam, or a temperate fluid as Oxidizer.

In the case of steam a pressure vessel is required, which would be a burden.

As for heating the Magnesium to a liquid, I felt that on the Moon, a deployable surround oven could heat up a Stainless Steel Magnesium tank, heat would be applied until the Magnesium is liquid, then the Oxidizer tank would be filled.  The oven retracted.

Then a launch.

Nothing that is currently in use.  But it would potentially be both a steam rocket and a chemical rocket at the same time.

VOID

From what I understand the combustion products would be Magnesium Oxide and Hydrogen.

As I recall that Hydrogen is a preferred propellant for Nuclear Fission Rockets, because of it's expansion characteristics, I am attracted to the notion that some of the output exhaust through the nozzle would include hot Hydrogen molecules.  And at the same time the Magnesium Oxide molecules would have greater inertia.  I hope that the Hydrogen vibrations (Expansion), would work favorable along with the heavier Magnesium Oxide molecules.

So, I hoped for a way to mass produce these machines (The hot fluids rockets), on the Moon, and to have it as a way to get lunar materials into orbit.  Those then to be recycled into orbital machinery of some kind(s).

Last edited by Void (2020-04-27 09:19:52)


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#35 2020-04-27 09:37:17

kbd512
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Posts: 4,893

Re: Physics Topics

tahanson43206,

Since the reason power is generated at all has to do with the flow of electrons through the electrical conductor when it moves through a magnetic field, I'm not sure I understand your question.  Electromagnetism is clearly involved, but it's the electrical conductor moving through a magnetic field that's generating the power.  Electrostatic discharge was the force that tore the conductor used in the TSS-1R experiment apart, not magnetism.

The tether from the TSS-1R experiment snapped due to some kind of human error, possibly with the way the tether was fabricated or deployed.  I can't recall what it was off the top of my head.  I do know that the tether wire was a leftover from the failed TSS-1 experiment.  The TSS-1R experiment was flown aboard STS-75.  In any event, exploding a thin wire with very high voltages is hardly a new phenomenon.

TSS-1R Mission Failure Investigation Board

In the end, about 180kg worth of wire generated about 3.5kWe (3,500V at ~1A) worth of power when almost fully deployed.  An equivalent CNT wire might be 36kg, IIRC, but it would have far greater tensile strength and temperature resistance (and the possibility of manufacturing it on-orbit, a doped CNT wiring with BNNT insulation "grown" aboard ISS, for example).  It's not going to compete with thin film PV for power output, but it could be very low cost and easier to package for deployment (paying out a spool of wire vs deployment of delicate thin films connected to PMAD connected to ion engines consuming expensive inert gas propellants).  PV will never provide propulsion on its own, so it's ultimately going to be cheaper and require less mass to deploy payloads to higher orbits using EMF since no propellant is required.  The Earth's magnetic field is always available, so I think we should use it to save mass and therefore money on propulsion.

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#36 2020-04-27 09:56:43

tahanson43206
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Re: Physics Topics

For kbd512 ... multiple items

First, thanks for Post #35 ... we are indeed talking about two different things, but ** I really like ** the path you've taken!

It has been a while since I've thought about the power generating potential of the upper reaches of Earth's atmosphere, so I appreciate your reminder of that possibility, and the experiments performed to date. 

Second ... your promotion from Moderator to Administrator has taken effect.  I've been updating the post in Housekeeping, but you may have read an earlier version of that post, or missed it altogether.

Third ... What this subtopic of the Physics topic is about is ...

Let me think about how to improve my presentation.  If you missed what I was trying to offer for consideration, then (most likely) everyone else would as well.

(th)

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#37 2020-04-27 10:28:15

kbd512
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Re: Physics Topics

Void,

H2 is the preferred propellant for NTR's because lighter molecules can be accelerated to higher velocities with a given amount of thermal input power, providing more specific impulse for a given amount of propellant mass.  More thrust could be provided with higher mass gas molecules, but specific impulse rapidly falls to chemical rocket levels as the mass of the propellant molecules increases.  At that point, you're better off not having to deal with the mass and radiation issues associated with operating the world's most powerful reactor crammed into a space the size of a garbage can and may as well get even higher thrust from ejecting even higher mass molecules produced by chemical reactions while you're at it.

If you're already on the moon and have enough power to refine metals, why not use solar power to heat a monopropellant gas like Oxygen, which you would have in abundance from refining all the metals present in the lunar regolith?  Keep the Magnesium to alloy with Aluminum, along with the water, for local uses.  Instead, collect the O2 from the metal refinery for use as a propellant in conjunction with beamed power, provided by the many tens of megawatts of power you'd already need to refine useful quantities of metals.  The Magnesium-based alloys are favorites for complex but lightweight and high strength parts, especially castings.  Aerospace alloys are hard to come by off-Earth, so my take on this is that you keep all of that stuff for fabrication of habitat modules or vehicle / computer / camera chassis.  Magnesium Diboride is also a material of interest to NASA and ESA for superconducting GCR shielding.  Various Mag-based alloys are also known to be good at suppressing EMI.

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#38 2020-04-27 11:50:12

Void
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Re: Physics Topics

KBD512,

I am entertained.  I would like to work with you and others on the topic of "Lunar Mass Lifting".  The moderater(s) can decide if this material can be placed into it's own topic.

You seem to believe that we should try to have propulsion as much as is plausible from the materials of greatest magnitude on the Moon.  I can agree, and would like to examine what they are.  I will put the numbers I have down now.  If you see errors, please tell me.

Oxygen      43%
Silicon        20%
Magnesium 19%
Iron            10%
Calcium        3%
Aluminum     3%
Manganese     .12%
Titanium         .18%

I do have propulsive notions for Oxygen, but so far not a Oxygen steam rocket.  You do appear to have such notions, which is OK.  Tough to do, I bet, but OK.

I would like to limit the magnitude of the required lifting task, by suggesting the utilization of three machines that will handle part of the load(s).

1) Ring Booster (Uses Hydrogen and Oxygen, or Methane and Oxygen, most likely)
2) Orbital Oxygen Propulsion Methods.  (There are several, I will get to the list soon).
3) Centrifuge Pulsing Oxygen Thruster (See "Spin Launch, and imagine timing pulses of Oxygen gas into a rotating thruster so that it exits in the 0-360 degree place where you want it to).

1) The "Ring Booster".  This is to assist a canister off of the surface of the Moon.  The canister could have it's own propulsion Mode as well, we have already each proposed something for that .  The ring booster could wrap around the canister, be attached to it and assist in the lift.
The other use for the ring booster is to bring things down such as Carbon, and substances to make alloys, and to fill other needs.

2) Orbital Oxygen Propulsion Methods: This could include an "Oxygen Mass Driver".  In my mind this would be a method to manufacture solid Oxygen bullets, and shoot them out of a mass driver, sequential magnets gun. (It is my belief that these collision hazards will be temporary, as I expect the bullets to evaporate fairly quickly).  The ESA has an air breathing ion rocket.  Perhaps it can handle Oxygen.  No firm information on that.  Vasimr Propulsion. Item #3, although intended to be a steering mechanism by me perhaps could be used as a sort of propulsion, perhaps to local navigation at a space station.  It might help to heat the Oxygen before it is pulsed into the centrifuge.

*Also possible would be a laser pointed at an Oxygen emitting nozzle.  I don't rule it out, but things get pretty complex for that at a distance.

3) Centrifuge Pulsing Oxygen Thruster: The Moon having it's own characteristics distinct from that of Earth or Mars, we can have permission to have a steering mechanism on the nose of our lifted canister.  It could spin like a airplane propeller, but pulses of Oxygen Gas, pre-heated or not, could be timed so that the Oxygen exits the centrifuge at some direction 0-360 degrees that is desired, for steering the object.  This will save on other consumables, such a burn thrusters or cold gas thrusters.

* I am going to propose a point to point objective for a non-landing device to take a big piece of the burden.  For now I am going to porpose a device that uses any of the items of #1, #2, and #3, that turn out to be the best practices.

L1 to Low Lunar Orbit.  #1 is marginally accepted as having some use in the transit under some notions.

Low Lunar Orbit, would be perhaps 50 miles/80.4672 km.   It just needs to clear the Lunar altitudes with reasonable assurance of not crashing.

The device that does this, will have solar panels.  I do not want to land them and lift them repeatedly from the Lunar surface.  It may have thrust methods, from item #2, one or more thrust methods.  They will probably expel Oxygen in some way or another.

As for the "Canister", it is my preference that it would have some lift method of it's own, and that it would likely be quite large, and that it will be able to bring a quantity of LOX to "L1".  It might be assisted in that by the "Ring Booster", and the L1<>Low Lunar Orbit electric propulsion device.  The canister itself upon arrival to L1 is also a delivered good.  Can then be used to build orbital machines, either as is with slight modification and add on devices, or by having it's materials re-cycled into something else.

So, I am thinking "Big" canisters.

Your method suggesting Oxygen as the propellant would be cleaner.  However, the method I suggested using Magnesium, allows for a propulsive chemical reaction.

There is quite a lot of Magnesium on the Moon it seems to me.  More than enough for any use desired.  (Hopefully my numbers for that are correct).

What do you think?

Done.

Last edited by Void (2020-04-27 16:46:20)


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#39 2020-04-27 16:50:20

Void
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Re: Physics Topics

Since I am not getting a response, then I will suggest that I am quite satisfied with two parts of the plan mentioned in the previous post.

But as far as the device to lift off the Moons surface to a mountain clearing orbit, I am thinking exotic methods are quite a way off, if ever.

So, for the "Big Canister(s)", I am willing to substitute something like the Space Shuttle External tank.  Either Hydrogen/Oxygen, or Methane/Oxygen.  At least one of them get us to relatively firm footing, but they may require that Hydrogen be provided from the polar deposits.  I still like the wrap around sort of toroidal booster, and expect it to use the same propellants as the canister would.  But the canister will be a one way device.

However parts of it might be two way.  You might bring back those parts that could be re-used.  Engines, AI, maybe centrifugal Oxygen thrusters.

At this time I am thinking about setting Methane aside, under certain conditions.  They are:
1) An extra-Lunar source of water ice. (Asteroids perhaps?)
2) A deep dark hole to drop the ice into at a reasonable speed of impact.  (Shadowed Craters)
3) A vehicle that can do that manipulation with the ice cube.  (I am hoping that the "Ring Booster" could be escorted to a landing run, by theL1<>Low Lunar Orbit electric propulsion device.)

Since I am cheep, I do not want to pay the full propellant price to deliver water to the Moons surface.  So, my hope is that on descent the "Ring Booster" would release the ice cube, and that although the "Ring Booster" would land at one of the favored sites near the lip of a shadowed crater, the ice cube would overshoot and impact inside of the shadowed crater.

Needless to say, the "Ice Cube" needs to be shaded from the sunlight during the entire flight.  Don't know what the potentials are for that.

While Hydrogen is not favored for a fuel tank these days for Earth or Mars, after all, part of my objective is to deliver big canisters to L1, with a load of LOX.  In that travel, I do not want all of the LOX consumed, so the LOX tank needs to be oversized.  I don't very much mind if all or most of the Hydrogen is consumed.  But then the "Internal Tank" is large, and that is what I want.  There is no air resistance, so the penalty for that is minimized.

My favorite use for those tanks would be to use them to construct synthetic gravity habitats.  And I would like quite a few of them to go to Mars orbit.

So, the Moons surface would be converted into a "Shop Floor", where canisters were mass produced along with Hydrogen and Oxygen.

Parts from the canister launches would be recycled back to the Moons surface.  The engines, AI, and perhaps centrifugal thrusters.

----

So, as I think of it just a little more, we do not have to fling ice cubes into dark craters, until the existing polar deposits become depleted, and that could be a long way off.

And....I think that if parts such as Engines, AI, and centrifugal thrusters are to be recycled, then they should be mounted permanently on the "Ring Booster".  The "Ring Booster" also needs propellant tanks sufficient for it to land itself back on the Moon.  But for assent, the canister should be it's supply of Hydrogen and Oxygen.

I think this is getting more closer to real possible.

The hope would be that some time from now either Magnesium using engines will be available, and/or Asteroid water.   But for now the above may do.

Last edited by Void (2020-04-27 17:26:35)


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#40 2020-04-27 18:27:29

tahanson43206
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Re: Physics Topics

For kbd512 re molecular bonds ...

I did not realize how quickly my opening question would lead to unfathomable depths ...

With the invention of Quantum Mechanics, around the time that Einstein was working on Relativity, the basis for understanding of molecular bonds was launched. Now (I gather) Quantum interactions are thought to be the mechanism by which atoms arranged in molecules are able to maintain cohesive attraction.  I had (somewhat naively to be sure) been depending upon a 50,000 foot level impression of how molecular bonds work, and since my day-to-day life did not depend upon understanding those bonds, I paid no further attention to them.

https://en.wikipedia.org/wiki/Molecular_orbital_theory

In chemistry, Molecular orbital (MO) theory is a method for describing the electronic structure of molecules using quantum mechanics. Electrons are not assigned to individual bonds between atoms, but are treated as moving under the influence of the nuclei in the whole molecule.[1] The spatial and energetic properties of electrons are described by quantum mechanics as molecular orbitals surround two or more atoms in a molecule and contain valence electrons between atoms. Molecular orbital theory, which was proposed in the early 20th century, revolutionized the study of bonding by approximating the states of bonded electrons—the molecular orbitals—as linear combinations of atomic orbitals (LCAO). These approximations are now made by applying the density functional theory (DFT) or Hartree–Fock (HF) models to the Schrödinger equation.
The other foundational theory of quantum chemistry is the valence bond theory.

Now, somewhat chastened, I am doubtful that my initial inquiry, about the magnetic component of electron interactions with atoms in molecules will lead anywhere.  It may well turn out that both the electric force and the magnetic force are equally involved in the quantum dance that allows atoms to form solids.

I'm doubtful I'm up to trying to learn this field.

I'm regretting I brought this up.

Edit#1:

https://en.wikipedia.org/wiki/Chemical_bond

Strong chemical bonds are the intramolecular forces that hold atoms together in molecules. A strong chemical bond is formed from the transfer or sharing of electrons between atomic centers and relies on the electrostatic attraction between the protons in nuclei and the electrons in the orbitals.
The types of strong bond differ due to the difference in electronegativity of the constituent elements. A large difference in electronegativity leads to more polar (ionic) character in the bond.

and …

Ionic bonding is a type of electrostatic interaction between atoms that have a large electronegativity difference. There is no precise value that distinguishes ionic from covalent bonding, but an electronegativity difference of over 1.7 is likely to be ionic while a difference of less than 1.7 is likely to be covalent.[8

This would appear to be elderflower’s bailiwick, but I am approaching it from the physics side  because I am asking the question … can magnetic force (somehow) add to the strength of electrostatic bonds between atoms in a solid?


(th)

Last edited by tahanson43206 (2020-04-27 18:52:25)

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#41 2020-04-28 09:31:42

kbd512
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Re: Physics Topics

Void,

My only belief about this is that refined metal is very hard to come by, no matter how abundant it may be in the crust of another planet.  Obtaining the ore is comparatively easy, but refining that ore into useful metal is very energy-intensive.  There's far more O2 than humans can breathe, so the next logical use for the O2 is as a nominal quantity rocket propellant.  The power required to refine enough Magnesium to use it and Oxygen, in multi-thousand ton quantities necessitated by a low-Isp rocket fuel, could just as easily be stored to use as part of an electromagnetic launch system (no atmosphere and thus no sonic booms nor atmospheric heating limitations placed upon making laps around an electromagnetic donut to achieve orbital velocity).  Electromagnetic launch, when combined with a monopropellant gas providing orbit circularization from a simple cold gas thruster and a battery-powered electrical heating element to superheat the O2 for a few seconds, almost negates the requirement to consume propellant to achieve orbit.

Electricity stored in flywheels is simply far more efficient for converting stored energy into propulsive force and most of the propulsion system remains on the surface of the moon, where humans living in a lunar colony (the only good reason to spend the money required to develop and construct any ISRU-based launch system) can much more easily maintain it (because stationary electric motors and flywheels are far easier and cheaper to maintain than severely life-limited rocket engines).  Here on Earth we have severe aerodynamic heating issues to deal with, but in a hard vacuum that primary impediment to implementation disappears.  The secondary impediment of contending with massive sound pressure waves is likewise non-existent.

There are so many other uses for high quality aerospace alloys that the power required to fabricate them is much more efficiently utilized as structures rather than as fuels.  Magnesium combined with Silicon Carbide nanoparticles produces an alloy that's one of the strongest known metal alloys, by weight, in existence.  Furthermore, Magnesium Oxide and Aluminum Oxide are frequently found in high quality ceramics used for eating / drinking utensils or cookware and as crucibles for melting metals.  If you can refine and use the precursor materials at all, then you'd most likely be making something of high intrinsic value with it.  For whatever reason, I just can't see us repeatedly burning thousands of tons of metals after expending the colossal amount of energy required to separate Magnesium from Oxygen.  If you could do that even once, then you have a substantial portion of the fabrication materials required by the electromagnetic launch system.  After it's set up, it just keeps paying you back each time you use it.

I'm not against experimenting with using metals from the moon as rocket fuels, but you have to understand that you're going to be locked into a perpetual cycle of trying to meet the energy requirement to produce propellants when you could store the energy required for far less total energy input, presuming the intent is to provide reliable and routine transport.

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#42 2020-04-28 10:38:38

Void
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Registered: 2011-12-29
Posts: 3,988

Re: Physics Topics

That's good information KDB512.

I am going to copy the materials that we recently generated for this subtopic, to another location and continue there. If you object to having your quotes copied as well, I will delete my quotes of your materials.  I will get out of the way of (th).

Index
» Science, Technology, and Astronomy
» Eventual Convergence?

Is where I will be on this topic.

Last edited by Void (2020-04-28 10:39:50)


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#43 2020-04-29 08:47:40

tahanson43206
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Re: Physics Topics

For Void re #42 ....

Best wishes for success with your new initiative in the Eventual Convergence? topic!

Your creativity is greater than the (apparent) capacity of the membership of the forum to keep up with.  We need new members who are seriously interested in practical planning for human living away from the Earth (as well as ON the Earth), and the many ideas you routinely generate would keep legions of serious people busy for many hours.

I remain interested in your balloon delivery idea, and hope to find time (and motivated people) to help develop it into a successful business.  It is SO much superior to the "traditional" high risk gamble-the-farm slow-down-in-the-atmosphere landing method I would expect it to ultimately become the generally accepted method of landing cargo and people on Mars.

In addition, I remain interested in your steam-rocket-escape-velocity-Moon idea, although it will require understanding of the physics of heating a body of water in a moving vehicle using track-side radiation (microwave/laser) that (apparently) is beyond the state of the art today.

As a reminder to anyone who happens upon this post, the challenge is to heat 51.5 kilograms of water to such a temperature (and therefore pressure) that a force of 245,000 Newtons will be generated by the boiler to impel the vehicle forward.

To accomplish this, the boiler would need to have features that (to the best of my knowledge) do not exist on Earth (or anywhere) at present.

Such a boiler would need to be transparent to whatever radiation is found most effective in heating that 51.5 kilograms of water.  Moreover, it would need to be strong enough to hold the pressure needed to generate that 245,000 Newtons.

It would indeed be rewarding to see ** this ** forum become a place where such a concept can be developed into a reasonable theory, and then extended to a practical application.

kbd512's vision of an electromagnetic launcher on the Moon is different in physics, but (to my mind) no less daunting.  There exists on Earth a working model of an electromagnetic launcher that reliably and repeatedly accelerates large masses (airplanes) to decent velocity (150 miles per hour) in a relatively short distance at 2.5 G's.  A lunar launcher would operate in exactly the same way for the first short distance.  However, in order to continue acceleration, the engineers designing the system would need to prove their ability to understand and master the challenges of accelerating that same mass over a much longer run.  It has been shown (elsewhere in the forum) that a run of 72 miles on the surface of the Moon, at a comfortable 2.5 G's, would deliver a vehicle to lunar escape velocity, and thus launch it toward the Earth or other destination.

It would indeed by rewarding to see such ideas continue to develop in ** this ** forum, and eventually reach practical application.

(th)

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#44 2020-04-29 12:42:36

Void
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Registered: 2011-12-29
Posts: 3,988

Re: Physics Topics

I will respond in the topic Eventual Convergence?


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#45 2020-04-30 09:07:10

tahanson43206
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Re: Physics Topics

A trade journal that arrived today included an offer of a free pdf on spectrum analysis.  If anyone is interested in seeing this industry generated paper, let me know.

An all-inclusive guide on the fundamentals of spectrum analysis.

Download this free guide to learn the fundamentals of spectrum analysis and its theoretical background and instruments.

Spectrum analysis (of course) is one of the leading tools used by astronomers for study of solar system objects.

However, I expect it would/will be a significant member of the tool kit of asteroid miners, who need to select where to invest time and resources most efficiently.

(th)

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#46 2020-04-30 18:43:35

tahanson43206
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Re: Physics Topics

This post is in support of a subtopic of the Physics topic.

https://www.visiontimes.com/2015/07/22/ … craft.html

The subtopic to which the article at the link above applies is the (hypothetical) steam powered rocket able to launch to escape velocity from the Moon.

The issue to be addressed is how to deliver energy from the side of the track to a moving vehicle so that 51.5 kilograms of water can be heated sufficiently to provide the boiler pressure sufficient to impart 245,000 Newtons of thrust to the vehicle.

The folks described in the article at the link above show a picture of a vehicle fitted with a microwave absorbing heat exchanger.

I will attempt to find out if there are any working examples of such a device.

Edit#1:

The heat-exchanger is simply a microwave-absorbent structure through which propellant flows in small channels. Nuclear thermal thrusters are based on an analogous principle, using neutrons rather than microwaves, and have experimentally demonstrated specific impulses exceeding 850 seconds.

The Microwave Thermal Thruster Concept - Core

There appears to be a downloadable pdf at the site from which the extract above was taken.
(th)

Last edited by tahanson43206 (2020-04-30 19:06:13)

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#47 2020-05-02 08:38:40

tahanson43206
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Re: Physics Topics

This is a new subtopic of the Physics topic.

SearchTerm:MagneticCable

A preliminary and definitely cursory search of available resources (books on hand, online articles) indicates (to me at this point) that the strength of a physical cable, such as might be constructed for use as a space elevator, is entirely due to electrostatic force.

The strength of a bond between two atoms (as nearly as I can tell at this point) is a function of the manner in which electrons in adjacent atoms share the space between the two nuclei.  It appears that when two like atoms approach each other, the electrons of each can be (and are) attracted to the positive charge in the nucleus of the other, and those electrons can (and do) release energy in order to nestle more closely together.

Hopefully, over time, this subtopic will attract the attention (and most importantly) contributions, of others who have a better grounding of this phenomenon.

However, for the purposes of ** this ** subtopic, the hypothesis set I will propose consists of two elements:

1) All known physical cohesion is characterized exclusively by expression of the electrostatic force <<== This should be knowable from available research
2) It is possible to add magnetic force to a physical structure (ie, a cable) so that the strength of the cable is increased over that of electrostatic force alone.

(th)

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#48 2020-05-04 10:19:02

tahanson43206
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Re: Physics Topics

Update start: 2020/05/04

This is a subtopic of the Physics topic: Lunar Escape Horizontal Launch

SearchTerm:LastSecond
SearchTerm:LunarLaunch

Two technologies are under consideration:
1)kbd512's electromagnetic launcher based on US Navy catapult design
2)Void's steam rocket launcher concept using external energy input

Specifications for the launch scenario:
1)Track length 72 miles (116 km)
2)Acceleration: 2.5 G's
3)Starting vehicle mass: 10,000 kg
4)Lunar escape velocity: 2.38 km/s
5)Launch run time: 97 seconds

For purists in he audience, the mass of the vehicle WILL increase due to relativistic effects, but for the purposes of this topic, that increase can be neglected. However, if someone would care to do the math, I'll be happy to post the result:

(answer) <<== if a forum member supplies this value I will edit it into this post.

For the ELM, more energy will be required, because the mass of the vehicle will not change during the launch.  Energy required to accelerate the ELM vehicle during the last second of the launch is:

(answer) <<== if a forum member supplies this value I will edit it into this post

For the steam rocket, 5000 kb is arbitrarily assigned for propellant, so the mass of the vehicle delivered to escape velocity is 5000 kg.  Energy required to accelerate the steam rocket vehicle during the last second of launch is:

(answer) <<== if a forum member supplies this value I will edit it into this post

The purpose of ** this ** post is to examine the last 1 second of launch from the two systems, with a view to trying to understand the technical challenge facing engineers who might be assigned to design teams.  The reasoning here is that if the problem of accelerating during the last second is solved, then the solutions for the previous 96 seconds will be less severe.

At the beginning of the last second of launch, the vehicle will be travelling:
Answer: <<== if a forum member supplies this value I will edit it into this post

In the case of the steam rocket, 51.5 kg of water is to be given sufficient energy to deliver 245000 Newtons of thrust.
Answer: <<== if a forum member supplies this value I will edit it into this post

Energy required to produce the desired result must be delivered from trackside equipment using electromagnetic radiation.  It is assumed that MASER or LASER projection equipment will be required, or perhaps both.

The required energy is to be delivered to the steam rocket boiler must pass through material capable of accepting external radiatiant energy while holding steam pressure of: (answer) <<== if a forum member supplies this value I will edit it into this post

(th)

Last edited by tahanson43206 (2020-05-04 12:07:53)

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#49 2020-08-19 10:10:10

tahanson43206
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Re: Physics Topics

Question for GW Johnson re Centripetal Acceleration

The presenter at the YouTube link below explains the mathematical derivation of Acceleration = Velocity Squared divided by Radius

https://www.youtube.com/watch?v=XgkzeUxChKU

It is that equation (I presume) you used to suggest a radius of 56 meters for a space habitat to deliver 1 g of simulated gravity at 4 RPM.

After watching the video carefully, (as well as another similar one) I am coming away with a feeling that while the mathematics is clear, the underlying physics of the forces at work is still not clear (to me at least).

The situation is similar to that of a ball swung at the end of a string ... The force needed to keep the ball in the air is felt by the operator.

That force (it seems to me) is the result of the operator pulling on the ball, which would otherwise continue in a straight line.

By any chance, are you familiar with a video that explains acceleration in those terms?

F = MA comes to mind .... The force on the string felt by the operator is a result of the mass of the ball (discounting the string for the moment) and the acceleration that pulls the ball away from the default straight line and bends it into a circle around the operator.

The context for this inquiry is the ongoing development of two different spaceship designs elsewhere in the forum.

Edit#1: After thinking about the situation for a while, I've come to realize that the mass of the object being accelerated is irrelevant. The amount of force required to bend its path will have a direct relationship to the mass of the object, but that too is irrelevant to the question of acceleration.

I suspect I've been confusing acceleration with force, and the investigation of what it's going to take to design a space craft able to provide useful simulated gravity has caused that confusion to become clear.

** Real ** gravity (curvature of space-time) does ** not ** cause a sensation of force in an object, whereas simulated gravity ** does ** cause a sensation of force as the object being accelerated is resisted by the floor of the habitat (in this case).

And right ** there ** is an illustration of another misunderstanding .... an object just above the surface of the Earth is pulled toward the center of the Earth.

The force that is doing that pulling is felt.  It's just that we humans are so used to it it is possible to forget it's there most of the time.

On the ** other ** hand, if we are in the ISS, which is in a state where centripetal force is exactly balanced with the pull toward Earth, we do ** not ** experience the force of gravity as we would if we were standing on Earth.

Edit#2: The observation about ** real ** gravity being "curvature of space time" led me to another (sort of) insight over night ...

A rotating habitat would be creating a "curvature of space time".  The objects involved are experiencing a constant acceleration away from the focal point of the curve.  The floor of the habitat prevents the objects from flying off into space.

The surface of the Earth prevents objects from descending into the body of the Earth. 

(th)

Last edited by tahanson43206 (2020-08-20 07:28:05)

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#50 2020-08-21 10:46:39

tahanson43206
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Re: Physics Topics

This might (possibly) be of interest to kbd512 ...

I'm not sure what to make of it ...

ABSTRACT
The calculation of the radial coupling between the nuclear motion and the electronic structure which induces charge transfer at low energy is discussed, and the utility of the force operator form for computing the coupling between large configuration-interaction wave functions is demonstrated. Many properties suggest that such couplings will be useful in constructing the diabatic scattering states; the agreement with available matrix elements computed numerically is excellent.

Received 13 August 1979
DOI:https://doi.org/10.1103/PhysRevA.23.1

©1981 American Physical Society

Nuclear fission appears to me (at this point of limited knowledge) to be a primitive energy source, capable of delivering nothing more useful than heat.

I recognize that neutrons and other particles emitted during fission may have value, but they are intermediate stages in a series of steps that ultimately leads to something useful.

The paper at the link above combines the words "nuclear" and "electronic", so I am left wondering if it describes a natural phenomenon that can deliver movement of electrons in an external circuit as a direct result of nuclear fission.

Since no such phenomenon has been reported (that I know of) in 70+ years of fission research, I have to assume it is not likely.

Fusion, on the other hand, appears to offer direct delivery of electron movement, but (of course) fusion is not yet self-sustaining (except in burst mode).

(th)

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